The specific aims of the studies proposed in each of the five research units are related in a broad sense to the cardiovascular responses to exercise. Dr. Longhurst will investigate the mechanisms of activation of single unit ischemically and reperfusion sensitive cardiac sympathetic and vagal afferents by reactive oxygen species. Dr. Kaufman will be investigating the contribution of central command and the exercise presser reflex to single unit sympathetic outflow to regional vascular beds (skin, muscle and kidney). Dr. Bonham proposes to study facilitative interactions between area postrema neurons and baroreceptor or cardiopulmonary afferents in the nucleus tractus solitarius (NTS), the potential contribution of neurons in the parabrachial nucleus and the potential neurotransmitters/neuromodulator(s) involved in the interactions. Dr. Kappagoda will investigate the role of pulmonary vagal afferents in transmitting information to the central nervous system during pulmonary congestion and edema. Dr. Stebbins will determine the role of vasopressin in the spinal cord and area postrema in modulating the cardiovascular response to muscle contraction. All studies propose to use electrophysiological and pharmacological approaches to investigate muscle, heart and lung reflexes and central neural integration important in regulation of the cardiovascular and respiratory systems during normal (e.g., exercise) and pathological conditions (i.e., myocardial ischemia, heart failure and hypertension).